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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

A Monte Carlo study of magnetic pairing mechanisms in high temperature superconductors

Bromley, Stefan January 1998 (has links)
No description available.
32

Modélisation multi-échelle des comportements plastiques et viscoplastiques des géomatériaux polycristallins / Multi-scale modeling of plastic and viscoplastic behavior of polycrystalline geomaterials

Zeng, Tao 12 December 2012 (has links)
La plupart des géomatériaux sont hétérogènes à différentes échelles matérielles. Le comportement mécanique macroscopique de ces matériaux dépend directement de la composition minéralogique et de la microstructure ainsi que leurs évolutions. Cette étude fait un simple essai d'étendre le modèle polycristallin le plus largement utilisé en métallographie à un type de matériaux géologiques quasi-fragiles : le granit. La fonction de charge standard et le potentiel plastique sont modifiés pour tenir compte des principales caractéristiques mécaniques des géomatériaux, e.g. la sensibilité à la pression et la dilatance plastique. Ce modèle d'auto-cohérence d'abord proposé par Hill est adoptée pour relier les champs locaux et ceux globaux. La réponse du macropolycristal est déterminée par le procédé d'homogénéisation classique. La mise en œuvre de la procédure numérique de stress microscopique et macroscopique est donnée et les éventuelles difficultés rencontrées sont mis en évidence. L'identification de sept paramètres micromécaniques est brièvement décrite. La validité du modèle développé est vérifiée par la comparaison entre les prédictions du modèle et les données expérimentales sur le test conventionnels et aussi sur le test traditionnel -- compression triaxiale. / Most geomaterials are heterogeneous material at different scales. The macroscopic mechanical behavior of these materials depends directly on the mineralogical composition and microstructure as well as their evolution. The present study makes a simple trial to extend the most widely used polycrystalline model in metallography to a typical quasi-brittle geological material--granite. The standard yield criterion and plastic potential are modified to consider the main mechanical features of geomaterial, e.g. pressure sensitivity and plastic dilatancy. The full self-consistent model firstly proposed by Hill is adopted to relate the local fields and overall ones. And the macro response of polycrystal is determined by the classical homogenization process. The numerical implementation of local and macro stress update procedure are given and the possible difficulties encountered are pointed out. The identification of seven micromechanical parameters is briefly described. The validity of the developed model is checked through the comparisons between model's predictions and experimental data on both conventional and true triaxial compression tests, respectively.
33

Trestný čin opilství podle § 360 tr. zák. / The crime of habitual drunkenness under s. 360 of the Criminal Code

Velich, Roman January 2011 (has links)
The crime of habitual drunkenness under s. 360 of the Criminal Code The purpose of this thesis could be summarized as a complex analysis of a crime of habitual drunkenness under s. 360 of the Czech Criminal Code. The described crime (sometimes named 'rauschdelikt᾿) represents one of possible approaches to a problematic question: How to hold a perpetrator who has committed a crime in mental state of insanity (irresponsibility), in which he had induced himself by use of alcohol, narcotics or similar substances, liable? As far as conformity with elementary principles of criminal law (such as 'nullum crimen sine culpa᾿) is concerned, the crime of habitual drunkenness seems to be the most suitable answer to the previous question. The crime of 'rauschdelikt᾿ is an old legal institute that is specific in many aspects. I have chosen the topic within the context of recent recodification of substantive criminal law. A previous regulation of this crime was often criticised for many reasons (e.g. improper title, too stringent penal sanction etc.). Thus we can now review if those criticised deficiencies have been set right. The thesis is divided into ten chapters. Chapter One is introductory and defines basic terminology used in the thesis, such as 'insanity᾿, 'culpability᾿ and so on. The third subchapter...
34

Global Optimization Methods based on Tabu Search / Globale Optimierungsmethoden, basierend auf Tabu-Suche

Stepanenko, Svetlana January 2008 (has links) (PDF)
This work encompasses three parts. The first part provides a concise review of the most prominent metaheuristic concepts currently available and gives essential preliminaries together with definition of the combinatorial optimization problems. It substantiates the choice of the investigation direction and basis idea of the developed methods. In the second part the new nonlinear global optimization routines based on the TS strategy are described. The new approaches are the Gradient Tabu Search (GTS), the Gradient Only Tabu Search (GOTS), and the Tabu Search with Powell’s Algorithm (TSPA). In the last part of the work the GOTS is applied for such chemical optimization problems. The chapter provides a systematic approach how the variables are chosen and the adjustable parameters are set. As test cases the global minimum energy conformation of some amino acids, of two angiotensin converting enzyme (ACE) inhibitors, of 2-acetoxy-N,N,N-trimethylethanaminium, and of a HIV-1 protease inhibitor is determined. / Die Arbeit umfasst drei Kapitel. Das erste Kapitel stellt eine kurze Zusammenfassung über die bekanntesten, zurzeit verwendeten Metaheuristischen-Konzepte dar und gibt notwendige Einleitungen zusammen mit der Definition der kombinatorischen Optimierungsprobleme. Das Kapitel begründet die Wahl des Tabu-Ansatzes und diskutiert die Basisideen der entwickelten Methoden. Im zweiten Kapitel werden die neuen entwickelten, nichtlinearen Optimierungsroutinen beschrieben, die auf Tabu-Suchstrategien beruhen. Die neuen Algorithmen sind Gradient Tabu Search (GTS), Gradient Only Tabu Search (GOTS) und Tabu Search with Powell’s Algorithm (TSPA). Das letzte Kapitel der Arbeit beschreibt die Anwendung der GOTS Methode auf dieses Problem. Diskutiert werden die Auswahl der Variablen und die Einstellung der justierbaren Parameter. Die Effizienz der GOTS Methode wird an Hand einiger Aminosäuren, zwei Angiotensin-Derivaten (ACE-Hemmer), des Acetylcholin und eines HIV-1-Protease-Hemmstoff gezeigt.
35

On Quasi-Volume-Filling Surfaces

Liu, Pan 24 April 2012 (has links)
The purpose of this paper is to construct a Quasi-volume-filling surface and study its properties. We start with the construction of a volume-filling surface, the Pólya surface, based on Pólya's curve, by rotating the Pólya's curve in 3-dimensional space. Then we construct a Quasi-space-filling curve in 2-dimensions, the Quasi- Pólya curve, which approximates the Pólya's curve and fills a triangle up to a residual small surface of arbitrary size. We prove that the Quasi-Pólya curve satisfies the open set condition, and there exists a unique invariant (self-similar) measure consistent with the normalized Hausdorff measure on it. Moreover, the energy form constructed on Quasi-Pólya curve is proved to be a closed & regular form, and we prove that the Quasi-Pólya curve is a variational fractal in the end. Next, we use the same idea, by rotating the Quasi-Pólya curve in 3-dimensional space, to construct the Quasi-Pólya surface, which is a Quasi-volume-filling surface and approximates to Pólya surface in some sense.
36

Influence of the Quasi-biennial Oscillation on Interannual Variability in the Northern Hemisphere Winter Stratosphere

Anstey, James Alexander 23 September 2009 (has links)
Observations show that the interannual variability of the Northern Hemisphere (NH) extratropical winter stratosphere is strongly correlated with the quasi-biennial oscillation (QBO) of tropical stratospheric winds, particularly during early winter. Most current general circulation models (GCMs) do not exhibit a QBO and therefore do not represent this important mode of tropical-extratropical interaction. In this study we examine the QBO-extratropical correlation using a 150-year GCM simulation in which a QBO occurs. Since no external forcings or interannual variations in sea surface temperatures are imposed, the modelled tropical-extratropical interactions represent an internal mode of atmospheric variability. The QBO itself is spontaneously forced by a combination of resolved and parameterized waves. The effects of this QBO on the climatological mean state and its interannual variability are considered, both by comparison with a control simulation (also 150 years in length, but with no QBO) and by compositing winters according to the phase of the QBO. Careful attention is given to the definition of QBO phase. Comparisons of the model results with observations (reanalysis data) are also made. QBO-induced changes in the climatological state of the model are found to have high statistical significance above the tropopause. In the extratropical winter stratosphere, these mean-state changes arise predominantly from the influence of the QBO on the propagation and dissipation of planetary-scale waves. This behaviour is shown to depend on the seasonal cycle, which argues for the usefulness of considering tropical-extratropical interactions in a GCM context. QBO influence on the interannual variability of the extratropical winter stratosphere is also seasonal, and the tropical-extratropical interaction is sensitive to the phase alignment of the QBO with respect to the annual cycle. This phase alignment is strongly affected by the seasonality of QBO phase transitions, which - due to the QBO being spontaneously generated, rather than having an imposed period - is somewhat realistic in the model. This leads to fluctuations in the strength of the modelled tropical-extratropical interaction occurring on a decadal timescale as an internal mode of atmospheric variability.
37

Quasi-homogeneous gold and bimetallic nanoparticle catalysts

Hou, Wenbo 13 August 2008
The research in this thesis involves the synthesis and characterization of nanoparticle catalysts for oxidation reactions. It includes two projects: 1) polymer-stabilized Au, Pd and bimetallic AuPd nanoparticle catalysts for alcohol oxidation reactions, and 2) oxidative stabilities and catalytic activities of thiolate- and dithiolate-protected Au monolayer-protected clusters (MPCs).<p>n the first project, alcohol oxidations under mild conditions using polyvinylpyrrolidone (PVP)-stabilized Au, Pd and bimetallic AuPd nanoparticle catalysts in aqueous solutions have been investigated. The catalytic activities of the nanoparticles towards the oxidation of benzyl alcohol, 1-butanol, 2-butanol, 2-buten-1-ol and 1,4-butanediol indicate that bimetallic 1:3 Au:Pd nanoparticles have higher catalytic activities than Au, Pd and other bimetallic AuPd nanoparticles, and that selectivities towards specific products can often be tuned using bimetallic particles. In addition, advantages and disadvantages for the use of such nanoparticle catalysts as mild, environmentally-friendly oxidation catalysts have been examined. This work has recently been published in the Journal of Catalysis.<p>In the second project, 1-dodecanethiolate-, dithiolate-, and 1:1 mixed 1-dodecanethiolate/dithiolate-protected Au MPCs have been synthesized and their thermal stability, oxidative stability in the presence of oxygen and cyanide anions have been studied. These systematic investigations reveal the stability of Au MPCs can be tuned by choosing different thiolate ligands and oxidation conditions. Partially-oxidized thiolate-protected Au MPCs which have substrate-accessible surfaces and are stabilized by residual thiolate ligands show indications they will be promising catalysts. The catalytic activities of 1-dodecanethiolate-, dithiolate-, and 1:1 mixed 1-dodecanethiolate/dithiolate-protected Au MPCs for catalytic 4-nitrophenol reduction with sodium borohydride were investigated, and all the Au MPCs showed high catalytic activity for this reaction.
38

Influence of the Quasi-biennial Oscillation on Interannual Variability in the Northern Hemisphere Winter Stratosphere

Anstey, James Alexander 23 September 2009 (has links)
Observations show that the interannual variability of the Northern Hemisphere (NH) extratropical winter stratosphere is strongly correlated with the quasi-biennial oscillation (QBO) of tropical stratospheric winds, particularly during early winter. Most current general circulation models (GCMs) do not exhibit a QBO and therefore do not represent this important mode of tropical-extratropical interaction. In this study we examine the QBO-extratropical correlation using a 150-year GCM simulation in which a QBO occurs. Since no external forcings or interannual variations in sea surface temperatures are imposed, the modelled tropical-extratropical interactions represent an internal mode of atmospheric variability. The QBO itself is spontaneously forced by a combination of resolved and parameterized waves. The effects of this QBO on the climatological mean state and its interannual variability are considered, both by comparison with a control simulation (also 150 years in length, but with no QBO) and by compositing winters according to the phase of the QBO. Careful attention is given to the definition of QBO phase. Comparisons of the model results with observations (reanalysis data) are also made. QBO-induced changes in the climatological state of the model are found to have high statistical significance above the tropopause. In the extratropical winter stratosphere, these mean-state changes arise predominantly from the influence of the QBO on the propagation and dissipation of planetary-scale waves. This behaviour is shown to depend on the seasonal cycle, which argues for the usefulness of considering tropical-extratropical interactions in a GCM context. QBO influence on the interannual variability of the extratropical winter stratosphere is also seasonal, and the tropical-extratropical interaction is sensitive to the phase alignment of the QBO with respect to the annual cycle. This phase alignment is strongly affected by the seasonality of QBO phase transitions, which - due to the QBO being spontaneously generated, rather than having an imposed period - is somewhat realistic in the model. This leads to fluctuations in the strength of the modelled tropical-extratropical interaction occurring on a decadal timescale as an internal mode of atmospheric variability.
39

Contrasting classical and quantum theory in the context of quasi-probability

Ferrie, Christopher Scott January 2008 (has links)
Several finite dimensional quasi-probability representations of quantum states have been proposed to study various problems in quantum information theory and quantum foundations. These representations are often defined only on restricted dimensions and their physical significance in contexts such as drawing quantum-classical comparisons is limited by the non-uniqueness of the particular representation. In this thesis it is shown how the mathematical theory of frames provides a unified formalism which accommodates all known quasi-probability representations of finite dimensional quantum systems. It is also shown that any quasi-probability representation is equivalent to a frame representation and it is proven that any such representation of quantum mechanics must exhibit either negativity or a deformed probability calculus. Along the way, the connection between negativity and two other famous notions of non-classicality, namely contextuality and nonlocality, is clarified.
40

Using TPR Method in Teaching English Adjectives

Ye, Zhen January 2011 (has links)
The topic of this study is using Total Physical Response (TPR) in teaching English adjectives to 11-year-old pupils. The objective of this study is to investigate whether the TPR method is effective in teaching English adjectives. The researcher used a quasi-experiment to design this study. The population was the pupils aged 11 in a middle school in Kristianstad. 30 pupils were selected as samples and divided into two groups: one experimental group and one control group. The steps of this experiment were: (1) the experimental group was taught by the TPR method; (2) the control group and the experimental group were given the same post-test. In order to investigate whether there is a necessity to adopt new English vocabulary teaching technique for these pupils, two questionnaires were deliberated; the first questionnaire was for all testees and the second questionnaire was just for the experimental group. The result of the study showed the pupils’ achievements in the experimental group were improved by the TPR method. The mean score of the experimental group was much higher than that of the control group. The p-value of this test was 0.0002 less than 0.01 which showed strong evidence that the results were not achieved coincidentally. The effect size of this study was 2.59 more than 0.8 which indicated that the TPR method has significant effectiveness in teaching English adjectives. The questionnaires indicated that TPR was the new English vocabulary teaching technique that the pupils need.

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